Insulator.



PATENTED'JUNE 7, 1904. G. G. GHESNE-Y.

IN SULATOR.

APPLICATION FILED AUG. a. 1003.

N0 MODEL.

WITNESSES 7? z, de -4 w.

INVENTOR. Cam/771225 6. (fie-spy.

A TTORNE).

UNITED STATES Patented June '7, 1904.

PATENT OFFICE.

CUMMINGS C. CHESNEY, OF PITTSFIELD, MASSACHUSETTS, ASSIGNOR TO STANLEY ELECTRIC MANUFACTURING COMPANY, OF PITTSFIELD, MASSACHUSETTS, A CORPORATION OF NET/V JERSEY.

INSULATOR.

SPECIFICATION forming part of Letters Patent No. 761,760, dated June 7, 1904.

Application filed August s, 1903.

To all whom, it may concern.-

Be it known that I, CUMMINGS C. Ci-IEs Y, a citizen of the United States, and a resident of Pittsfield, Massachusetts, have invented certain new and useful Improvements in Insulators, of which the following is a specification.

My invention relates to insulators for electric conductors, and particularly for those conductors carrying current of high potential; and its object is to provide a structure in which there is less danger of arcing from the conductor to the cross-arm or support than in insulators as formerly constructed. In order to increase the resistance to creepage or surface discharge, it has been customary to build high-potential insulators with a number of petticoats, thus increasing the creeping, distance. In wet weather, however, with insulators of this type there is danger of an are forming directly from the outer periphery of one petticoat to the petticoat below. it, and thence to the cross-arm. This is due to the water dripping from the upper petticoat onto or near the lower one, and thus affording a passage for the current. By my invention this danger is greatly reduced by anovel proportioning and arrangement of the petticoats.

In the drawing, A B C represent the three petticoats, forming an insulator mounted on pin D. The insulator may be formed of three pieces cemented or fused together in any wellknown manner, as indicated in the drawing, or may be formed of a single piece.

In order to avoid arcing from the periphery of petticoat A to petticoat B, the latter instead of being practically the same diameter as A is made considerably smaller in diameter, so that the water dripping from A falls clear of B. On the other hand, petticoat B is of sufliciently large periphery to prevent any leakage directly to petticoat C and to discharge any water which may fall upon it due to a driving rain well outside of the periphery of C. In order that the periphery of B may be far enough removed from water dripping from A and yet extend far enough beyond C to discharge the water at a safe distance from C, B is formed with a maximum diameter Serial No. 168,698. (No inodel.)

' about half-way between the maximum diameter of A and the diameter of C in the hori- Zontal plane of the periphery of B. Furthermore, in order to provide the greatest protection against arcing from one part of the insulator to another it is necessary that every part to which an arc is likely to form be as far as possible from the part from which the arc is likely to spring. In order to obtain this condition, the upper surfaces of the petticoats near their periphery are formed as shown in the drawing. It will be seen in the drawing that the upper surface of B near its periphery forms a concave curve closely ap- 7 proximating the arc of a circle drawn around.

the periphery of A as a center. Thus the points on the upper surface of B upon which water is likely to be blown in dripping from the edge of A are equidistant from the edge of A, and thus the maximum protection against arcing is obtained. C is formed both as regards its diameter and shape of its upper surface in the same'relation to B that B bears to A. Thus the edge of C is approximately equidistant from a straight line dropped from the edge of B and from the pin, while its upper surface near its edge forms a concave curve closely approximating the are of a circle drawn around the edge of B as a center. Thus the long leakage path of the ordinary petticoat type of insulator is obtained, while the danger of arcing from the edge of one petticoat to another is reduced to a minimum.

I do not desire to limit myself to the particular construction and arrangement of parts here shown, since changes therein which do not depart from the spirit of my invention and which are Within the scope of the appended claims will be obvious to those skilled in the art.

Having thus fully described my invention, I claim as new and desire to protect by Letters Patent- 1. In an insula'tona plurality of petticoats, the upper surface of a petticoat being concave and all points on said surface near its edge being approximately equidistantfromthe edge of the upper adjacent petticoat.

Lil

2. In an insulator, a plurality of petticoats, a section in a vertical radial plane of the upper surface of a petticoat forming a curve approximating near the edge of said surface the arc of a circle drawn from the edge of the upper adjacent petticoat as a center.

In an insulator, a plurality of petticoats, the diameter of each petticoat being less than that of the one above it, and all points on its upper surface near its edge being approximately equidistant from the edge of the petticoat above it, said upper surface being concave.

4:. In an insulator, a plurality of petticoats, the edge of one of said petticoats being ap proximately half-way between a vertical line dropped from the edge of the upper adjacent petticoat and the outer periphery of the lower adjacent petticoat measured in the horizontal plane of the first-named edge, the upper surface of said petticoat being concave.

5. In an insulator, a plurality of outwardlyextending petticoats arranged one above another, one of said petticoats having an upper surface formed in a concave curve, and having a maximum diameter approximately half the sum of the maximum diameter of the upper adjacent petticoat and the diameter of the lower adjacent petticoat measured in the plane of the edge of the first petticoat.

Signed at Pittsiield, Massachusetts, this 4th day of August, 1903.

CUMMINGS U. CHESNEY.

IVitnesses:

L. A. HAwKINs, R. E. HAYNES. 

